One aspect of the proposed work is to synthesize tripeptides of the type Asn-X-Ser/Thr, where X is any amino acid residue. Thus we will prepare peptides in which X is a charged amino acid (Lys, Asp) or a very hydrophobic one (Phe, Tyr). This tripeptide will be tested as substrate for the oligosaccharide-lipid transferase. A second aspect will be to study the topological orientation of the oligosaccharide-lipid in purified R.E.R. In addition the site of transfer of the oligosaccharide chain from oligosaccharide-lipid to protein will be studied.